Lamina Junction Research Articles

The Anatomical and Biomechanical Superiority of Novel Posterior En Bloc Elevation Cervical Laminoplasty.

Objectives. In this study, we performed a novel type of posterior en bloc elevation cervical laminoplasty (PEEL) to keep the integrity of the posterior structure, aiming to reduce axial symptoms complicated by a conventional cervical laminoplasty procedure. Methods. Twelve human cervical cadaveric spines (C2-T1) were sequentially tested in the following order: intact condition, open-door laminoplasty (ODL) through bilateral intermuscular approach (mini-invasive ODL), PEEL, and laminectomy (LN). After bilateral transecting at the junction of lamina and lateral mass through the tubular retraction system, the PEEL procedure symmetrically elevated all the posterior structure which was further stabilized with bone grafts and titanium plates. Computed tomography (CT) scan and biomechanical testing were performed after each condition. Results. Both mini-invasive ODL and PEEL procedures were accomplished with 2 small incisions on each side. Two types of laminoplasties could enlarge the spinal canal significantly both in cross-sectional area and anteroposterior diameter comparing with intact condition. The PEEL procedure demonstrated a significantly higher enlargement rate on a canal area and a symmetrical expansion pattern. Compared with intact condition, mini-invasive ODL performed from C3-C7 demonstrated significantly decreased motion in all testing directions except the flexion range of motion (ROM); the PEEL procedure showed mild and insignificant decrease on ROM in all directions. Laminectomy resulted in a statistically significant increase in all directions except the lateral bending ROM. Conclusions. Posterior en bloc elevation cervical laminoplasty can enlarge the canal more effectively and preserve better ROM after operation than the ODL procedure. Although technically challenging, the PEEL procedure probably would decrease the common complications associated with ODL laminoplasty.

Spinous Process-Splitting Hemilaminoplasty for Intradural and Extradural Lesions

ObjectiveTo describe a novel spinous process-splitting hemilaminoplasty technique for the surgical treatment of intradural and posterior epidural lesions that promotes physiological restoration.MethodsThe spinous process was split, the area of the facet lamina junction was drilled, and en bloc hemilaminectomy was then performed. After removing intradural and posterior epidural lesions, we fitted the previously en bloc-removed bone to the pre-surgery same shape, and held it in place with non-absorbable sutures. Surgery was performed on 16 laminas from a total of nine patients between 2011 and 2014. Bony union of the reconstructed lamina was assessed using computed tomography (CT) at 6 months after surgery.ResultsSpinous process-slitting hemilaminoplasty was performed for intradural extramedullary tumors in eight patients and for ossification of the ligament flavum in one patient. Because we were able to visualize the margin of the ipsilateral and contralateral dura, we were able to secure space for removal of the lesion and closure of the dura. None of the cases showed spinal deformity or other complications. Bone fusion and maintenance of the spinal canal were found to be perfect on CT scans.ConclusionThe spinous process-splitting hemilaminoplasty technique presented here was successful in creating sufficient space to remove intradural and posterior epidural lesions and to close the dura. Furthermore, we were able to maintain the physiological barrier and integrity after surgery because the posterior musculature and bone structures were restored.

The insertion technique of translaminar screws in the thoracic spine: computed tomography and cadaveric validation

Background contextTranslaminar screws can be a good salvage technique in some cases of severe deformities, infection, tumor, osteoporosis, and revision cases with altered anatomy. To our knowledge, the insertion technique for translaminar screws in the thoracic spine has not been studied. PurposeTo suggest a safe insertion technique of translaminar screws in the thoracic spine. Study designA cadaveric study. MethodsFifteen cadaveric spines were harvested from T1 to T12, and 1-mm computed tomography (CT) scans and three-dimensional reconstructions were obtained to rule out any bony anomaly. Eleven of the cadaveric spines were separated at each level from T1 to T12 (Group S) and four were not separated (Group N-S). Translaminar screws were inserted into every level along the trajectories proposed by the previous studies. The screw diameter was determined based on the reference article. For T1–T6, the screw diameter selected was 4 mm, and for T7–T12, a 3.5-mm diameter screw was used instead. The entry point for the 1° screw was at a distance equal to the diameter of the desired screw above the inferior margin of the spinolaminar junction. To create the trajectory, a drill guide was inserted at the entry point and directed toward the middle portion of the base of the transverse process of the contralateral side and was followed carefully to not break the inner/outer cortex of the lamina. The length of the drilled hole, representing the trajectory of the screw made by the drill guide, was measured, and the 1° screws were inserted according to the length measured. The entry point for the 2° screw was at a distance equal to the diameter of the screw below the superior margin of the base of the spinous process and lamina junction. The drill guide was pointed toward the inferior angle of the contralateral junction of the rib and the vertebra along the slope of the contralateral lamina. The 2° screw was inserted in the same manner as previously described. The 2° screw diameter was downsized if there was not enough space because of the 1° screw. For each vertebra from the 11 separated cadaveric spines, inner or outer cortex breakage was checked visually. For the remaining four nonseparated spines, CT scans were used to find any inner or outer cortex breakage. ResultsThirty-three vertebral levels were abandoned from Group S because of altered anatomy (eg, fusion, fracture during separation, anatomical anomaly of having only 11 thoracic spine segments). Out of 147 vertebral levels, there was no vertebra that did not allow screw insertion. No specimen required using smaller diameter 2° screw because of blockage of the 1° screw. There was no cortical breakage by the screws in Group S. In Group N-S, CT scan showed four inner cortex breakages and three outer cortex breakages, all of which were slight cortical breakages. There were no facet injuries due to the screws in Group N-S. There was no blockage of the ribs during screw placement in all specimens, and the drill guide could lean against the rib for guidance because the angle of the rib and the opposite lamina tended to be the same. ConclusionsTranslaminar screws can be inserted relatively safely in the thoracic spine. For the 1° translaminar screw, the entry point is at a distance equal to the diameter of the desired screw superior to the inferior margin of the lamina-spinous process junction. The trajectory should be targeted toward the center of the base of the contralateral transverse process. For the 2° translaminar screw, the entry point is at a distance equal to the diameter of the desired screw below the superior margin of lamina-spinous process junction, and the target is the inferior angle of the junction of the rib and vertebra on the contralateral side.

Permineralized Alethopteris ambigua (Lesquereux) White: A medullosan with relatively long-lived leaves, adapted for sunny habitats in mires and floodplains

Permineralized Alethopteris ambigua (Lesquereux) White occurs in the Kalo Formation (Moscovian, Pennsylvanian) of Iowa. The following characteristics distinguish A. ambigua from other permineralized Alethopteris species: narrow pinnule width, a deeply sunken midrib having a round cross-section, deep midline depth, and a thick lamina that is not enrolled. Both the new permineralized Alethoptheris from the Kalo Formation and adpressed A. ambigua (Lesquereux) White have ‘pecopteroid’ pinnules with lamina that are linked at the base. Because the midrib of A. ambigua is round in cross-section, the widest part of the midrib lies below the midrib–lamina junction. In adpression this configuration would produce the ‘midrib flanges’ found in adpressed A. ambigua from Missouri. Three Alethopteris species with narrow pinnules and pecopteriod insertion have been extensively synonomized by previous workers: A. ambigua (Lesquereux) White, Alethopteris friedelii P. Bertrand, and Alethopteris lesquereuxii Wagner. Together with Alethopteris leonensis Wagner, these four species form a morphological continuum similar to other alethoperid morphological continua (e.g. the Alethopteris densinervosa, Alethopteris ingbertensis, Alethopteris lonchitifolica, Alethopteris missouriensis, Alethopteris westphalensis continuum). Nonetheless, because their permineralized forms can be readily distinguished, we favor retention of both A. ambigua (Lesquereux) White and A. lesquereuxii Wagner.Most permineralized mire alethopterids, with the exception of Alethopteris sp. from the Lewis Creek deposit (Kentucky, U.S.A.), have anatomical features consistent with foliage that grew in sunny, wet or humid habitats, including thick photosynthetic lamina, thick cuticle and enrolled edges. Most permineralized mire neuropterids, with the exception of Laveineopteris rarinervis from the Illinois Basin, have anatomical features consistent with foliage that grew in shady, wet or humid habitats, including thin photosynthetic lamina, and thin cuticle. In seed-ferns with broadly attached pinnules and compound leaves, lamina thickness/pinnule width (LT/MaxW) is a proxy for leaf mass per area (LMA), and indicates the relative economic cost and longevity of medullosan foliage. Measures of LT/MaxW for mire medullosans suggest that most mire alethopterids produced metabolically-expensive, long-lived fronds, whereas most mire neuropterids produced metabolically-cheap, short-lived fronds.

Cadaveric position of unilateral vocal cord: a case of cricoid fracture with ipsilateral arytenoid dislocation

We report a case of cricoid cartilage fracture with unilateral arytenoid dislocation following a motorcycle accident. This 25 year old male sustained blunt injury to the head, face and neck. He presented late to the hospital with one week history of dysphonia. Laryngoscopy revealed cadaveric position of the non-functioning left vocal cord. CT and MRI showed laterally displaced left vocal cord. Displaced fractures were noted in the cricoid at the junction of lamina with the anterior arch on the left side and at the right side of the anterior arch, along with dislocated left arytenoid resulting in ipsilateral vocal cord palsy. Medialization thyroplasty was performed to improve his phonation. Laryngeal trauma warrants close monitoring because of the risk of airway compromise. Radiologists play a crucial role in early diagnosis and should always have high index of suspicion. Recognition of laryngeal injury is important for initial resuscitation as well as for long term airway and vocal function.

Morphometric analysis of the thoracic pedicle: An anatomico-radiological study

Knowledge of the morphometric anatomy of the pedicles in thoracic spine is essential for the surgeon attempting thoracic pedicle screw placement. To study the morphometry of the pedicles in the thoracic spine in Indian subjects and note the anatomical landmarks required for safe and accurate pedicle screw placement. An anatomico-radiological study with cadaveric confirmation was conducted in a medical college and tertiary care center. Morphometric anatomy of 720 pedicles from T1-T12 was studied. The study consisted of 15 separated thoracic vertebral cadavers and 15 computed tomographic scans of undiseased thoracic spine. Transverse and sagittal pedicle diameters, transverse pedicle angle, chord length and the pedicle entry point landmarks were studied. Using the results, accuracy of the pedicle screw placement was confirmed in 120 pedicles from five unseparated cadavers. Transverse pedicle diameter was narrowest at T4 and gradually increased craniocaudally. Twenty-two percent of the pedicles from T4 to T6 were less than 4.5 mm, but none were less than 3.5 mm. The transverse pedicle angle was widest at T1 (26.50) and decreased caudally to T12 (8.10). The chord length gradually increased caudally from a minimum of 30.4 mm at T1 to a maximum of 43.3 mm at T12. Landmarks (transverse and vertical distance) for the pedicle entry point were measured from the reference point taken as the center of the junction of lamina and the transverse process. The pedicle entry point was always superolateral to this reference point. Knowledge of the pedicle diameter and chord length is essential for choosing the appropriate pedicle screw, whereas the pedicle angle and the entry point are important for accurate screw placement.

Modified Trajectory of C2 Laminar Screw - Double Bicortical Purchase of the Inferiorly Crossing Screw

The crossing laminar screw fixation might be the most recently developed approach among various fixation techniques for C2. The new construct has stability comparable to transarticular or transpedicular screw fixation without risk of vertebral artery injury. Quantitative anatomical studies about C2 vertebra suggest significant variation in the thickness of C2 lamina as well as cross sectional area of junction of lamina and spinous process. We present an elderly patient who underwent an occipito-cervical stabilization incorporating crossed C2 laminar screw fixation. We preoperatively recognized that she had low profiles of C2 lamina, and thus made a modification of trajectory for the inferiorly crossing screw. We introduce a simple modification of crossing C2 laminar screw technique to improve stability in patients with low laminar profiles.

The effects of combined x-axis translations and y-axis rotations on projected lamina junction offset

Objectives: To quantify the projection errors caused by the combining of selected x-axis translations with selected y-axis rotations as seen on plain film anteroposterior (AP) radiographs. Study Design: A computer was used to model the projection of the lamina junction and points on the lateral body margins of a 2-dimensional vertebral model onto an AP radiograph. This simulation was done in the neutral position and in a number of combinations of x-axis translations and y-axis rotations. Results: Some combinations of x-axis translation and y-axis rotation can increase or decrease the projected horizontal lamina offset as compared with what would be found with rotation alone. The projection of some combinations may lead the viewer to believe that rotation of the vertebral model is in the opposite direction of its true rotation. Conclusion: The projections of combined movements of x-axis translations and y-axis rotations can lead to confusion when the clinician attempts to discern quantity and direction of y-axis vertebral rotation from the AP radiograph. (J Manipulative Physiol Ther 2001;24:509-13)

Cervical coupling during lateral head translations creates an S-configuration

Objective. To determine cervical coupling during the posture of lateral head translation relative to a fixed thoracic cage. Design. Digitized measurements from anteroposterior cervical radiographs of 20 volunteers were obtained in neutral, left, and right lateral translation posture of the head compared to a fixed thorax. Background data. Clinically, lateral translation of the head is a common posture. Ranges of motion and spinal coupling have not been reported for this movement. Methods. Vertebral body corners, mid-lateral articular pillars and the superior spinous–lamina junction of C3–T4 were digitized on 60 radiographs. Using the orthogonal axis of positive x-direction to the left, vertical as positive y and anterior as positive z, digitized points were used to measure projected segmental z-axis rotation, y-axis rotation, and segmental lateral translations of each vertebra. Results. Subjects translated their heads laterally a mean of 51 mm. The major coupled motion was lateral bending ( z-axis rotation), which changed direction at the C4–C5 disc space creating an S-shape. Upper cervical (C3–C4) lateral bending was contralateral to the main motion of head translation direction. Lower cervical and upper thoracic lateral bending were ipsilateral. Other segmental motions averaged less than 1 mm and 1°. Conclusions. Lateral head translations ( x-axis) compared to a fixed thoracic cage can be large with a mean of 51 mm to one side. The major spinal coupling was lateral bending which changed direction at C4–C5 resulting in an S-configuration. This might have application in side impacts. All other segmental movements were small, less than 1 mm and 1°. Relevance The clinically common posture of lateral head translation results in an S-shaped cervical spine and may occur in side impact trauma. This posture has not been studied for cervical coupling patterns or range of motion (ROM).

Correlation and quantification of projected 2-dimensional radiographic images with actual 3-dimensional y-axis vertebral rotations

Background: Historically, measurement of 2-dimensional (2-D) radiographic images on the anteroposterior radiograph has been made to assess 3-dimensional (3-D) y-axis vertebral rotations. Objectives: To correlate and quantify measurements of the projected 2-D radiographic image with the degree of 3-D y-axis rotation. Study design: A computer model was positioned in a simulated x-ray beam. Points of model contact with the simulated beam were projected onto a line in the neutral position and the first 7 degrees of both positive and negative y-axis rotation using two different axes of rotation. A larger model, a shape-altered model, and a decreased source-object-distance model were also studied. Results: 3-D y-axis rotation of vertebrae causes an off-center displacement of the 2-D projected lamina junction in relation to the projected vertebral body. The magnitude of displacement increases with increasing degrees of rotation. In our model, no clinically significant difference was found in the amount of the projected off-center displacement of the lamina junction between either of our two chosen axes of rotation. However, significant differences in the projected offset were found between vertebrae with the same degree of rotation as a result of changes in vertebral shape, size, and positioning. The projected lamina junction offcentering at a given rotation is quantified for our model. Conclusion: Use of millimetric measurement of the projected lamina offset on the anteroposterior radiograph is an inaccurate method for the assessment of the degree of 3-D y-axis vertebral rotation. (J Manipulative Physiol Ther 1999;22:21–5)

Three dimensional surgical simulations of the spine

A finite element model of a complete vertebra has been formulated. It is used to simulate the laminectomy and Harrington rod procedures. The results indicate that high tensile stresses occurred on the affected side in the region of the pars interarticularis after laminectomy. High tensile stresses near the pars interarticularis and at the posterior junction of lamina and pedicles are predicted due to Harrington rod loading.

Observations on the afferent and efferent connections of the avian isthmo-optic nucleus

The efferent and afferent connections of the avian isthmo-optic nucleus (ION) were studied using light microscopic techniques. Injections of [ 3H]proline into the nucleus resulted in labeling of centrifugal endings in the retina at the junction of the inner plexiform layer and inner nuclear layer, but produced no other transported label to any thalamic or mesencephalic nucleus. The origin of the tectal afferents to the ION was demonstrated by means of injections of [ 3H]proline into the most superficial layers of the optic tectum and by stereotaxic injections of horseradish peroxidase into the ION. The tectal efferent cell bodies were located in lamina h of the optic tectum and at the junction of laminae h and i.

THE ROLE OF THE LIGULE IN SUGARCANE TAXONOMY

American Journal of BotanyVolume 38, Issue 2 p. 144-146 Article THE ROLE OF THE LIGULE IN SUGARCANE TAXONOMY Ernst Artschwager, Ernst Artschwager U.S.D.A. Field Station, State College, New MexicoSearch for more papers by this author Ernst Artschwager, Ernst Artschwager U.S.D.A. Field Station, State College, New MexicoSearch for more papers by this author First published: 01 February 1951 https://doi.org/10.1002/j.1537-2197.1951.tb14805.xCitations: 2AboutPDF ToolsRequest permissionExport citationAdd to favoritesTrack citation ShareShare Give accessShare full text accessShare full-text accessPlease review our Terms and Conditions of Use and check box below to share full-text version of article.I have read and accept the Wiley Online Library Terms and Conditions of UseShareable LinkUse the link below to share a full-text version of this article with your friends and colleagues. Learn more.Copy URL Share a linkShare onFacebookTwitterLinkedInRedditWechat No abstract is available for this article.Citing Literature Volume38, Issue2February 1951Pages 144-146 RelatedInformation